See response #7 above. And yes, an MSD is a standard porta potti, with a fitting so a pumpout can be added. But that fitting is removeable so a pour spout can be used.
And when you go to the Bahamas, you'll need it because with the exception of Nassau I found zero pumpout facilities. Which I found strange since the waters there are what they sell as an attraction.
You are correct, I did find the dual outlet model, but it makes no difference down there. As I posted yesterday, I called the contractor that maintains the free pump out vessels and services for Monroe County, and he explained that they would not hook up to ANY portable devise. I told him it would be easy for me to briung out to the cockpit so that it could be connected. He reiterated that NO, it must be a through hull, plumbed type 2 or 1 MSD or they won't touch it. It would be convenient yes, but frightfully expensive to install on a Cat 22 or other small craft. The second issue is that once installed, the system now falls under the USCG regulations, unlike a non connected portable, they inspect and certify the system carefully, as they consider it to be more likely to leak raw sewage than a self contained. Bad news for many. It would be great to be able to use the stations rather than only state parks, - anchor, carry, dump, clean, etc. As for the earlier accounts of Boot Key policy, as soon as I began to explain what had been said here, he interrupted and finished my sentence with a sarcastic "Boot Key Harbor". Apparently they are well known to the locals, he a 19 year live-aboard resident, for policy that is native only to them. It is all unfortunate news for many, especially since a recent audit found that the contractor received TWICE the amount per pump out last year than the contract originally called for. One would think that for $46 a pop, they would be more accommodating to the boaters that bring down $$$ for the area. Like the contents under discussion, it STINKS!